There are a number of surgical techniques for treating clouding within the eye lens, which is referred to as a cataract in medicine. The most common technique is phacoemulsification, in which a thin needle is introduced into the diseased lens and excited to vibrate by means of ultrasound. The vibrating needle emulsifies the lens in its direct vicinity in such a way that the created lens particles can be suctioned away through a line by means of a pump. In the process, a rinsing fluid (irrigation fluid) is supplied, with the particles and the fluid being suctioned away through an aspiration line, which is usually arranged within the needle. Once the lens has been completely emulsified and removed, a new artificial lens can be inserted into the empty capsular bag, and so a patient treated can thus regain good visual acuity.
Approximately 600,000 surgical procedures of this type are carried out each year in Germany alone. The rate of complication is relatively low, but this requires much experience of the performing surgeon. Furthermore, the time expenditure for emulsifying an eye lens is still relatively high. In order to be able to shorten the time needed for the surgical procedure, it is possible to let the vibrating needle operate at a higher amplitude. If this occurs without interruption, this is synonymous with a higher energy input. However, the result of this is greater heating in the vicinity of the vibrating needle. Since the needle is pierced through the cornea, a higher energy input means a stronger thermal load on the cornea. This can lead to at least partly surrounding tissue, such as, for example, the cornea, overheating and being damaged. By contrast, if the surgeon works with a needle which is only operated at a small amplitude such that there is only a small energy input into the lens and the surrounding tissue, the risk of damage to the tissue can be reduced. However, the duration of the surgical procedure then increases accordingly. If a relatively hard eye lens is present, the surgeon can only achieve emulsification by a higher energy input. However, in order to prevent burning of the tissue such as the cornea there must be frequent interruptions during the surgical procedure so that enough time is available for a cool-down.